Q. What is Bitcoin?
A. Bitcoin is a peer-to-peer currency. Peer-to-peer means that no
central authority issues new money or tracks transactions. These tasks
are managed collectively by the network.

Q. How does Bitcoin work?
A. Bitcoin utilises public-key cryptography. A coin contains the owner's
public key. When a coin is transferred from user A to user B, A adds B's
public key to the coin, and the coin is signed using A's private key. B
now owns the coin and can transfer it further. A is prevented from
transferring the already spent coin to other users because a public list
of all previous transactions is collectively maintained by the network.
Before each transaction the coin's validity will be checked.